Abstract: Man's Impact on Global Sedimentary Cycles of Metals
Fred T. MacKenzie, Ronald J. Lantzy
Predictive global models of the sedimentary cycles of metals show that enrichment factors for the metals in northern and southern hemispheric dusts are similar and related to man's emissions of these metals to the atmosphere. Our interpretation of this relation, based on a model of interhemispheric transfer rates, is that anthropogenic contributions have affected significantly the distribution of metals in both the northern and southern hemisphere.
Metals with high volatility, like mercury, arsenic, and selenium, are transported through the atmosphere in significant quantities, and are delivered to the oceans dissolved in rain and in the dissolved and suspended load of rivers. Because of the high volatilities of these metals, man's contributions to their cycles on a global basis rival natural fluxes. However, evaluation of fluxes into and out of the oceans suggests little impact of man's contributions on oceanic metal concentrations by the year 2000.
Metals with low volatility, like iron and manganese, have atmospheric fluxes that are minor in comparison to other fluxes and are transferred from the continent to the ocean mainly in river-borne suspended material. For these metals man's contributions to natural cycles are small and generally local.
We conclude that prediction of man's impact on metal contributions on the global environment necessitates evaluation of (1) the natural sedimentary cycle of metals, including all known reservoirs, transfer paths, and fluxes; and (2) kinetic and thermodynamic controls on processes involving the metals.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC